Poly(butylene-co-adipate terephthalate), method of manufacture, and uses thereof

ABSTRACT

A method for preparing poly(butylene terephthalate-co-adipate) copolymer includes reacting (i) poly(butylene terephthalate-co-adipate) oligomers, wherein the oligomers comprise at least one polymer residue derived from a polyethylene terephthalate component and a quencher, with (ii) a chain extender under conditions sufficient to form the poly(butylene terephthalate-co-adipate) copolymer.

BACKGROUND OF THE INVENTION

This disclosure relates to biodegradable aliphatic-aromatic copolyestercompositions, and methods of manufacture of the copolyesters andcompositions. These copolyesters and compositions are useful as moldedor extruded plastic objects, films, and fibers.

Aliphatic-aromatic copolyesters are often used for the manufacture ofbiodegradable disposable articles. For example, U.S. Pat. No. 6,020,393discloses a branched, random aliphatic-aromatic copolyester suitable forforming into biodegradable disposable articles, includingpoly(butylene-co-adipate terephthalate) (PBAT). U.S. Pat. No. 6,201,034discloses processes for preparing PBAT by reacting dimethylterephthalate (DMT) or terephthalic acid (TPA) and adipic acid (AA) withbutanediol (BDO). The biodegradability is induced by the incorporationof adipic acid in poly(butylene terephthalate) (PBT). The polymer thusmade has a typical melting point (T_(m)) of about 109° C., and a glasstransition temperature (Tg) between −25 to −30° C. The polymerization isconducted using a transesterification (TE) catalyst such as a titaniumor tin compound.

The present inventors have observed that biodegradablealiphatic-aromatic copolyester product obtained in such a reaction wasdiscolored, often ranging from pink to red in color. This presents aproblem in that the aesthetic appearance of a non-white polymer productis an obstacle to employing the polymer in end-uses where thediscoloration is apparent and cannot be readily overcome or masked withpigments, whitening agents or fillers. It has further been found that itis difficult to achieve a white color while at the same time maintainingor improving upon other desirable properties of biodegradablealiphatic-aromatic copolyesters such as PBAT. For at least the foregoingreasons, there remains a long unfelt need to develop processes thatproduce useful biodegradable aliphatic-aromatic copolyesters.

SUMMARY OF THE INVENTION

In an embodiment, a method is provided for preparing poly(butyleneterephthalate-co-adipate) copolymer, the method comprising reacting (i)poly(butylene terephthalate-co-adipate) oligomers, wherein the oligomerscomprise at least one polymer residue derived from a polyethyleneterephthalate component selected from polyethylene terephthalate,polyethylene terephthalate copolymers, and combinations thereof, and aquencher selected from a phosphorus-containing compound, anitrogen-containing compound, a boron-containing compound, andcombinations thereof, with (ii) a chain extender selected from apolyisocyanurate, polyisocyanate, isocyanate and combinations thereofunder conditions sufficient to form the poly(butyleneterephthalate-co-adipate) copolymer, wherein the copolymer has a meltingtemperature of 100 to 120° C.; a number average molecular weight of atleast 30,000 g/mole; an intrinsic viscosity of at least 1.0; a Tg of −30to −10° C., and the copolymer comprises a residue derived from thepolyethylene terephthalate component.

In another embodiment, a method for preparing poly(butyleneterephthalate-co-adipate) copolymer having a melting temperature of 100to 120° C. comprises reacting 1,4-butanediol and adipic acid in thepresence of a catalyst under conditions sufficient to form poly(butyleneadipate) oligomers; adding a polyethylene terephthalate component to thepoly(butylene adipate) oligomers in the presence of 1,4-butane diol atatmospheric pressure or greater, at a temperature from 190° C. to 270°C., under an inert atmosphere, under conditions sufficient todepolymerize the polyethylene terephthalate component to form thepoly(butylene terephthalate-co-adipate) oligomers; adding 0.05 to 1 mole% of a quencher selected from a phosphorus-containing compound, anitrogen-containing compound, a boron-containing compound, andcombination thereof, to the poly(butylene terephthalate-co-adipate)oligomers, based on the moles of catalyst; and reacting the oligomerswith 0.01 to 5 mole % of a chain extender selected from apolyisocyanurate, polyisocyanate, isocyanate, and combinations thereofunder conditions sufficient to form the poly(butyleneterephthalate-co-adipate) copolymer having a melt temperature of 100 to120°, and comprising at least one residue derived from the polyethyleneterephthalate component.

Another method for preparing poly(butylene terephthalate-co-adipate)copolymer having a melt temperature of 100 to 120° C. comprises:reacting (i) a polyethylene terephthalate component selected from thegroup of polyethylene terephthalate, polyethylene terephthalatecopolymers, and combinations thereof, with (ii) a diol componentselected from ethylene glycol, propylene glycol, and combinationsthereof, in a reactor at atmospheric pressure or greater, in thepresence of a catalyst component, under conditions sufficient todepolymerize the polyethylene terephthalate component into a firstmolten mixture; adding 1,4-butane diol and adipic acid to the moltenmixture in the presence of a catalyst component, under conditionssufficient to form a second molten mixture comprising oligomers; adding0.05 to 1 mole % of a quencher selected from a phosphorus-containingcompound, a nitrogen-containing compound, a boron-containing compound,and combinations thereof, to the poly(butylene terephthalate-co-adipate)oligomers, based on the moles of catalyst; and reacting the oligomerswith from 0.01-5 mole % of a chain extender selected from anisocyanurate, polyisocyanate, isocyanate and combinations thereof, underconditions sufficient to form the poly(butyleneterephthalate-co-adipate) copolymer having a melt temperature of 100 to120° C., and comprising a residue derived from the polyethyleneterephthalate component.

In another embodiment, a poly(butylene terephthalate-co-adipate)copolymer is provided having a melt temperature from 100 to 120° C.,wherein the copolymer comprises a residue derived from a polyethyleneterephthalate component selected from polyethylene terephthalate,polyethylene terephthalate copolymers, and combinations thereof; aquencher residue; and from 0.05 to 1 weight % of a residue of anisocyanurate, polyisocyanate, isocyanate and combinations thereof.

In another embodiment, a composition comprises the poly(butyleneterephthalate-co-adipate) copolymer; and at least one of an additiveselected from nucleating agents, antioxidants, UV stabilizers,plasticizers, epoxy compounds, melt strength additives, alcohols,acetates, alcohol-acetate copolymers, crosslinkers, anti-aging agents,retrogradation agents, anti-blocking agents, water, odor-controllingagents, and combinations thereof; and an additional thermoplasticpolymer.

An article is described, comprising the above-described compositions.

A method of forming an article comprising molding, coating, calendaring,shaping, or extruding the above-described compositions.

These and other features, aspects, and advantages will become betterunderstood with reference to the following description and appendedclaims.

DETAILED DESCRIPTION OF THE INVENTION

The present inventors have surprisingly found that apoly(butylene-co-adipate terephthalate) copolymer prepared by reactingpoly(butylene-co-adipate terephthalate) oligomers with a chain extenderhas an advantageous combination of properties. In a particularlyadvantageous feature, the poly(butylene-co-adipate terephthalate)oligomers are prepared by depolymerizing aromatic polyester, inparticular a polyethylene terephthalate homopolymer, copolymer, orcombination thereof by reaction with butane diol (BDO) and conductingin-situ reaction with adipic acid and a second dihydric alcohol. Use ofthe polyethylene terephthalate component an aromatic carboxylic acidsource allows recycle of scrap polyesters. Surprisingly, theadvantageous properties of the copolyesters are obtained even in thepresence of a residue from the aromatic polyester if a quencher is addedto the depolymerization mixture after the oligomers are formed.

The term “recycle” as used herein refers to any component that has beenmanufactured and either used or intended for scrap. Thus, a recyclepolyester can be polyester that has been used, for example in a drinkingbottle, or that is a byproduct of a manufacturing process, for examplethat does not meet a required specification and therefore wouldotherwise be discarded or scrapped. Recycle materials can thereforecontain virgin materials that have not been utilized. The polyethyleneterephthalate component from which the aliphatic-aromatic copolyester ismade can be in a variety of forms. Generally, in the case of PET, thePET component includes recycle (scrap) PET in flake, powder/chip, film,or pellet form. Before use, the PET is generally processed to remove anyimpurities such as paper, adhesives, polyolefin, e.g., polypropylene,polyvinyl chloride (PVC), nylon, polylactic acid (an aliphaticpolyester), and other contaminants.

The prefix “bio-” or “bio-derived” as used herein means that thecompound or composition is ultimately derived from a biological source,e.g., “bio-1,3-propane diol” is derived from a biological (e.g., plantor microbial source) rather than a petroleum source. Similarly, theprefix “petroleum-” or “petroleum-derived” means that the compound orcomposition is ultimately derived from a petroleum source, e.g., a“petroleum-derived poly(ethylene terephthalate) is derived fromreactants that are themselves derived from petroleum.

The singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise. “Or” means “and/or.”“Combinations thereof” is not limiting, and means that at least one ofthe named components is present, together with another of the namedcomponent or a component of like nature. Further unless definedotherwise, technical, and scientific terms used herein have the samemeaning as is commonly understood by one of skill in the art to whichthis invention belongs. Compounds are described using standardnomenclature. For example, any position not substituted by any indicatedgroup is understood to have its valency filled by a bond as indicated,or a hydrogen atom. A dash (“-”) that is not between two letters orsymbols is used to indicate a point of attachment for a substituent. Forexample, —CHO is attached through carbon of the carbonyl group.

The term “random copolymer,” as used in this application refers to acopolymer that includes macromolecules in which the probability offinding a given monomeric unit at any given site in the chain isindependent of the nature of the adjacent units.

Other than in the operating examples or where otherwise indicated, allnumbers or expressions referring to quantities of ingredients, reactionconditions, and the like, used in the specification and claims are to beunderstood as modified in all instances by the term “about.” Variousnumerical ranges are disclosed in this patent application. Because theseranges are continuous, they include every value between the minimum andmaximum values. The endpoints of all ranges reciting the samecharacteristic or component are independently combinable and inclusiveof the recited endpoint. Unless expressly indicated otherwise, thevarious numerical ranges specified in this application areapproximations. The term “from more than 0 to” an amount means that thenamed component is present in some amount more than 0, and up to andincluding the higher named amount.

All ASTM tests and data are from the 2003 edition of the Annual Book ofASTM Standards unless otherwise indicated.

With respect to the terms “terephthalic acid group,” “isophthalic acidgroup,” “ethylene glycol group,” “butanediol group,” and “diethyleneglycol group” being used to indicate, for example, the weight percent(wt. %) of the group in a molecule, the term “isophthalic acid group(s)”means the group or residue of isophthalic acid having the formula(—O(CO)C₆H₄(CO)—), the term “terephthalic acid group” means the group orresidue of isophthalic acid having the formula (—O(CO)C₆H₄(CO)—), theterm “diethylene glycol group” means the group or residue of diethyleneglycol having the formula (—O(C₂H₄)O(C₂H₄)—), the term “butanediolgroup” means the group or residue of butanediol having the formula(—O(C₄H₈)—), and the term “ethylene glycol group” means the group orresidue of ethylene glycol having the formula (—O(C₂H₄)—).

The butane diol, adipic acid, or any other component of the copolyesterscan be derived from a biological source. In an embodiment all or aportion of the butane diol is derived from a biological source.“Bio-derived diols” as used herein refers to alcohols other than thosenamed and derived from a biological source, e.g., various pentoses,hexoses, and the like.

The poly(butylene-co-adipate terephthalate) copolymers described hereincomprise adipic acid groups, butane diol groups, and aromaticdicarboxylic acid groups derived from the poly(ethylene terephthalate)component, i.e., a poly(ethylene terephthalate) homopolymer, apoly(ethylene terephthalate) copolymer, or a combination thereof. Inother words, the poly(butylene-co-adipate terephthalate) copolymerscontains aromatic dicarboxylic acid groups incorporated into thecopolyester from the depolymerization of the poly(ethyleneterephthalate).

Processes for preparing copolyesters by depolymerizing aromaticpolyesters in the presence of polyols are known in the art. For example,U.S. Pat. No. 5,451,611 describes a process for converting wastepolyethylene terephthalate to either poly(ethylene-co-butyleneterephthalate) or polybutylene terephthalate by reaction with BDO. Aprincipal objective of U.S. Pat. No. 5,451,611 was to provide a processfor converting PET waste directly to another high value polymer withoutbreaking down the PET to its constituent monomers or oligomers. Thepatent discloses numerous examples in which a variety of polymers have acombination of diols incorporated at various ratios of amounts. Example11 of U.S. Pat. No. 5,451,611 patent shows a PBT polymer being formedwith a complete replacement of EG by BDO. U.S. Pat. No. 5,266,601 andU.S. Pat No. 20090275698 (A1) describe a process for making PBT from PETby reacting PET with BDO.

The poly(butylene-co-adipate terephthalate) copolymers thereforecomprise isophthalic acid groups, terephthalic acid groups, andcombinations thereof derived from the PET component. The copolyestersfurther comprise other residues present in the poly(ethyleneterephthalate) component or arising from the depolymerization process,including catalyst residues from the manufacture of the poly(ethyleneterephthalate) component, residues from additives in the poly(ethyleneterephthalate) component, or residues arising from side reactions thatoccur during manufacture of the poly(ethylene terephthalate) componentand/or the reaction of the BDO, the adipic acid, and the poly(ethyleneterephthalate) component. For example, in addition to butane diolgroups, dihydric alcohol groups incorporated into the copolyester can bederived from any dihydric alcohol that reacts with the adipic acid andthe aromatic dicarboxylic acid to form the copolyester, such as groupsderived from ethylene glycol, 1,2-propylene glycol, 1,3-propyleneglycol, 1,2-butanediol, 2,3-butanediol, 1,4-butanediol, tetramethylcyclobutanediol, isosorbide, cyclohexane dimethanol (including 1,2-,1,3-, and 1,4-cyclohexane dimethanol), bio-derived diols, hexyleneglycols, and a combination thereof. In another embodiment, the dihydricalcohol is selected from 1,4-butanediol, 1,3-propanediol, ethyleneglycol, and combinations thereof. Such groups can arise, for examplefrom a polyethylene terephthalate component containing polyethyleneterephthalate copolymers.

Residues derived from the poly(ethylene terephthalate) component can beethylene glycol groups, diethylene glycol groups, antimony-containingcompounds, germanium-containing compounds, titanium-containingcompounds, cobalt-containing compounds, tin-containing compounds,aluminum, aluminum salts, 1,3-cyclohexanedimethanol isomers,1,4-cyclohexanedimethanol isomers, alkaline salts, alkaline earth metalsalts, phosphorus-containing compounds and anions, sulfur-containingcompounds and anions, naphthalene dicarboxylic acids, 1,3-propanediolgroups, or combinations thereof. In an embodiment, the residue derivedfrom the poly(ethylene terephthalate) component comprises ethyleneglycol groups, diethylene glycol groups, and more particularly acombination of ethylene glycol groups and diethylene glycol groups.

Accordingly, our invention includes embodiments in which the residuederived from the poly(ethylene terephthalate) component includesindividual elements and combinations of the foregoing materials. In anembodiment, the residue derived from the poly(ethylene terephthalate)component comprises the cis isomer of 1,3-cyclohexanedimethanol, cisisomer of 1,4-cyclohexanedimethanol, trans isomer of1,3-cyclohexanedimethanol, trans isomer of 1,4-cyclohexanedimethanol andcombinations thereof. In one embodiment, the residue derived from thepoly(ethylene terephthalate) component includes a combination ofethylene glycol and diethylene glycol groups, and can further comprisethe cis isomer of 1,3-cyclohexanedimethanol, the cis isomer of1,4-cyclohexanedimethanol, the trans isomer of1,3-cyclohexanedimethanol, trans isomer of 1,4-cyclohexanedimethanol, orcombinations thereof. In an embodiment, the residue derived from thepolyethylene terephthalate component comprises ethylene glycol groups,diethylene glycol groups, the cis isomer of cyclohexanedimethanol, thetrans isomer of cyclohexanedimethanol, and combinations thereof. In anembodiment, the residue derived from the poly(ethylene terephthalate)component comprises ethylene glycol groups, diethylene glycol groups,and cobalt-containing compounds The residues can be present in a totalamount from more than 0 to 10 wt. % of the copolymer, for example 0.01to 8 wt. %, 0.05 to 6 wt. %, 0.1 to 5 wt. %, 0.1 to 2.5 wt. %, or 0.1 to1.0 wt. % of the copolymer.

Catalysts effective to depolymerize the poly(ethylene terephthalate)component and form the oligomers are known, and include, for example,tin compounds, titanium compounds, and combinations thereof as well asmany other metal catalysts and combinations of metal catalysts that havebeen disclosed in the literature. Specific examples of catalysts forpolymerization and/or transesterification include antimony compounds,titanium isopropoxide, manganese diacetate, antimony oxide, dibutyl tindiacetate, zinc chloride, or combinations thereof. The amount ofcatalyst to obtain an acceptable depolymerization/oligomerization rateat the desired temperatures will vary, and can be determined byexperimentation. For example, the catalyst amount can be 1 to 1000, 1 to5000 ppm, or more, based on the weight of the poly(ethyleneterephthalate) component. In an embodiment, the catalyst is atetraisopropyl titanate, available from DuPont under the tradenameTYZOR.

Conditions effective to depolymerize the poly(ethylene terephthalate)component and form the oligomers can vary depending on the particularpoly(ethylene terephthalate) component, its purity, type of catalyst,amount of reactants, and like considerations, and can be determined byexperimentation. For example, the depolymerization can be conducted at atemperature from 150 to 300° C. under atmospheric or reduced pressureand inert atmosphere.

The poly(butylene-co-adipate terephthalate) oligomers are treated with aquencher prior to reaction with the chain extender, or at the same timethat the chain extender is added to the oligomers. The quencher can be aphosphorus-containing compound, a nitrogen-containing compound, aboron-containing compound, or a combination thereof.

Phosphorus-containing compounds include phosphoric acid, poly(phosphoricacid), phosphorous acid, monobutyl phosphate, dibutyl phosphate,monoalkyl phosphates, dialkyl phosphates, and combinations thereof.

Nitrogen-containing Nitrogen-containing compounds include alkyl amines,aromatic amines, alkyl aromatic amines, alkanol amines, ammoniumcompounds, and combinations thereof.

Boron-containing compounds include boric acid, boron alkoxides, boricoxides, boron halides, metaborates, monoalkyl borates, dialkyl borates,trialkyl borates, borazines, and combinations thereof.

Generally, the quencher is selected from phosphoric acid, phosphorousacid, boric acid, and combinations thereof.

In an embodiment of the method, the quencher is added to thepoly(butylene terephthalate-co-adipate) oligomers in an amount of 0.05to 1 mole % based on the moles of catalyst. In another embodiment of themethod, the amount of the quencher is from 0.05 to 1 mole %, based ontotal moles of terephthalic acid, adipic acid and 1,4 butanediol. In anembodiment, the poly(butylene terephthalate-co-adipate) copolymercontains 0.05 to 1 mol % of the quencher residue.

The poly(butylene-co-adipate terephthalate) copolymer is produced byreacting poly(butylene-co-adipate terephthalate) oligomer with a chainextender. In an embodiment, the chain extender is selected frommononuclear isocyanate, binuclear isocyanate, trinuclear isocyanate,tetra or higher nuclear isocyanate and their mixtures, diisocyanateselected from the group consisting of tolylene 2,4-diisocyanate,tolylene 2,6-diisocyanate, 2,4′ -diphenylmethane diisocyanate,naphthylene-1,5-diisocyanate, xylylene diisocyanate, hexamethylenediisocyanate, isophorone diisocyanate, and methylenebis(2-isocyanatocyclohexane).

In an embodiment, the chain extender is a combination comprising, basedon the total weight of the combination, from 45 to 80 wt. % of a chainextender selected from a mononuclear isocyanurate, a chain extendercontaining two functional groups that react with an end group of theoligomer, or combinations thereof; from 13 to 25 wt. % of a chainextender selected from a binuclear isocyanurate, a chain extendercontaining three functional groups that react with an end group of theoligomer, and combinations thereof; from 5 to 12 wt. % of a chainextender selected from a trinuclear isocyanurate, a chain extendercontaining four functional groups that react with an end group of theoligomer, and combinations thereof; and from 2 to 18 wt. % a tetra- orhigher-nuclear isocyanurate.

In an embodiment of the method, the poly(butyleneterephthalate-co-adipate) copolymers are prepared by reacting thepoly(butylene terephthalate-co-adipate) oligomers with 0.05 to 5 weight% of a chain extender selected from a polyisocyanurate, polyisocyanate,isocyanate, and combinations thereof. In an embodiment of thepoly(butylene terephthalate-co-adipate) copolymer, the chain extenderresidue can be present from 0.05 to 5 weight % based on total weight ofpoly(butylene terephthalate-co-adipate) copolymer. In another embodimentthe amount of chain extender can be present from 0.1 to 1 weight %.

Conditions for reacting the oligomers with the chain extender are knownin the art, and will depend on the specific reactants, their amounts,and desired reaction time. For example, the chain extension can beconducted in the melt, for example at 100 to 120° C. at atmospheric orreduced pressure, optionally under an inert atmosphere.

The poly(butylene terephthalate-co-adipate) copolymers have anadvantageous combination of properties. For example, the copolymers canhave a melt temperature of 105 to 125° C., 110 to 125°, 100 to 120° C.,100 to 115° C., or 100 to 110° C. The copolymers can have a Tg of −30 to−10° C., −25 to −10° C., or −20 to −10° C.

The copolymers can further be manufactured to have a desired numberaverage molecular weight, for example greater than 30,000 g/mole, 30,000to 300,000 g/mole, 40,000 to 200,000 g/mole, or 45,000 to 150,000g/mole.

In addition, the copolymers can have an I.V. of greater than 1.0,greater than 1.2, greater than 1.5 deciliter per minute (dL/minute) asmeasured in a 60:40 by weight phenol/1,1,2,2-tetrachloroethane mixtureat 23° C.

Specifically the copolymer has a melt temperature of 100 to 125° C.; anumber average molecular weight of at least 30,000 g/mole; an intrinsicof viscosity (I.V.) of at least 1.0 dL/minute; and a Tg of −30 to −10°C., and the copolymer comprises a residue derived from the polyesterresidue component. The manufacturing conditions can be adjusted toachieve the desired combination of properties. For example, thecopolymers can have a melt temperature of 100 to 115° C.; a numberaverage molecular weight of 40,000 to 200,000 g/mole; an intrinsic ofviscosity (I.V.) of at least 1.2 dL/minute; and a Tg of −25 to −10° C.Other combinations of properties within these ranges are possible.

The composition includes, in addition to the copolyesters as describedabove, other components combined with the copolyester, for example otherpolymers and additives, used in the formulation of molding compositions.Examples of the polymers include aliphatic polyesters, aromaticpolycarbonates, aliphatic polycarbonates, starches, aromatic polyesters,cycloaliphatic polyesters, polyesteramides, combinations thereof, andthe like. The polymers can be wholly or partially bio-derived, includingpetroleum-derived aromatic polyesters and bio-derived aromaticpolyesters. In the art, chain extenders such as epoxides, bisoxazolines,biscaprolactams, dianhydrides, and the like have been reported for usein polyesters. Among these, epoxides are most widely used on acommercial scale due to their relatively low cost and availability of avariety of structures.

In a specific embodiment the copolyester is combined with an aliphaticpolyester, for example poly(lactic acid), poly(hydroxyalkanoate),poly(butylene succinate), poly(butylene adipate), poly(butylenesuccinate adipate) and poly(caprolactone), or a combination thereof.Polyhydroxyalkanoates (PHAs) are linear polyesters produced in nature bybacterial fermentation of sugar or lipids, and include, for example,poly(R-3-hydroxybutyrate) (PHB or poly(3HB)).

In another specific embodiment the copolyester is combined with anaromatic polyester, for example a poly(trimethylene terephthalate)derived from petroleum-derived 1,3-propanediol, poly(trimethyleneterephthalate) derived from bio-derived 1,3-propanediol, poly(butyleneterephthalate) derived from petroleum-derived 1,4-butanediol,poly(butylene terephthalate) derived from bio-derived 1,4-butanediol,poly(trimethylene terephthalate) derived from post-consumerpoly(ethylene terephthalate), poly(butylene terephthalate) derived frompost-consumer poly(ethylene terephthalate), virgin poly(ethyleneterephthalate), recycled poly(ethylene terephthalate), post-consumerpoly(ethylene terephthalate), recycled poly(trimethylene terephthalate),recycled copolyesters of terephthalic acid with ethylene glycol andcyclohexane dimethanol, or a combination thereof.

The amounts of the copolyesters and the additives vary depending on thedesired properties of the biodegradable composition. In an embodimentthe additives are present in an amount from 2 to 90 wt. %, for examplefrom 2 to 40 wt. % or from 40 to 90 wt. %, based on the total weight ofthe composition. When the copolyester is used with starch, the amount ofstarch can range from 40 to 90 wt. %, and the amount of polyester canrange from 10 to 60%, based on the total weight of the totalcomposition. When the copolyester is used in conjunction with polylacticacid, the amount of the copolyester can range from 40 to 90 wt. % andthe amount of polylactic acid can range from 10 to 60 wt. %,specifically 40 to 60%, based on the total weight of the composition.

The composition can also contain from 0.01 to 45 wt. %, based on thetotal weight of the composition, of an additive selected from alcohols,acetates, alcohol-acetate copolymers, and combinations thereof.Additionally, the composition can contain from 0.01 to 2 wt. %, based onthe weight of the composition, of an additive selected fromcrosslinkers, anti-aging agents, retrogradation agents, anti-blockingagents, water, odor-controlling agents, and combinations thereof.

Additives ordinarily incorporated into polymer compositions can be used,with the proviso that the additives are selected so as to notsignificantly adversely affect the desired properties of thecomposition, for example, biodegradability, impact, flexural strength,color, and the like. Such additives can be mixed at a suitable timeduring the mixing of the components for forming the composition.Possible additives include impact modifiers, fillers, reinforcingagents, anti-oxidants, heat stabilizers, light stabilizers, ultravioletlight (UV) absorbers, plasticizers, lubricants, mold release agents,antistatic agents, colorants, blowing agents, flame retardants,anti-drip agents, and radiation stabilizers. Combinations of additivescan be used, for example an antioxidant, a UV absorber, and a moldrelease agent. The total amount of additives (other than any impactmodifier, filler, or reinforcing agents) is generally 0.01 to 5 wt. %,based on the total weight of the composition. In a specific embodiment,from 0.01 to 5.00 wt. % of a nucleating agent, antioxidant, UVstabilizer, plasticizers, epoxy compound, melt strength additive, or acombination thereof is used.

Advantageously, the copolyester and compositions containing thecopolyester can be biodegradable. This means that the copolyester andcompositions containing the copolyester exhibit aerobicbiodegradability, as determined by ISO 14855-1:2005. ISO 14855-1:2005,as is known, specifies a method for the determination of the ultimateaerobic biodegradability of plastics, based on organic compounds, undercontrolled composting conditions by measurement of the amount of carbondioxide evolved and the degree of disintegration of the plastic at theend of the test. This method is designed to simulate typical aerobiccomposting conditions for the organic fraction of solid mixed municipalwaste. The test material is exposed to an inoculum, which is derivedfrom compost. The composting takes place in an environment whereintemperature, aeration and humidity are closely monitored and controlled.The test method is designed to yield the percentage conversion of thecarbon in the test material to evolved carbon dioxide as well as therate of conversion. Also specified is a variant of the method, using amineral bed (vermiculite) inoculated with thermophilic microorganismsobtained from compost with a specific activation phase, instead ofmature compost. This variant is designed to yield the percentage ofcarbon in the test substance converted to carbon dioxide and the rate ofconversion. Generally, our copolyesters (and compositions containingcopolyesters) exhibit a biodegradation (measured in % of solid carbon ofthe test item that is converted into gaseous, mineral C in the form ofCO₂), which is at least 30% after 75 days. In one embodiment, thecopolyesters (and compositions containing copolyesters) exhibit abiodegradation, which is at least 40% or 50% after 75 days. Thebiodegradation of the copolyesters (and compositions containingcopolyesters) can range from at least 30% to 50%, or at least 30% to60%, or at least 30% to 70%.

Advantageously, useful articles can be made from the copolyester andcompositions containing the copolyester. In a specific embodiment, anarticle is extruded, calendared, extrusion molded, blow molded, solventcast or injection molded from the copolymer or the compositioncontaining the copolymer. The article can be a film or a sheet. When thearticle is a film, the article can be formed by extrusion molding orcalendaring the copolyester or composition containing the copolyester.The copolyesters and compositions containing the copolyesters are usefulfor films, for example film packaging applications, among otherapplications.

As stated above, various combinations of the foregoing embodiments canbe used. The invention is further described in the followingillustrative examples in which all parts and percentages are by weightunless otherwise indicated.

EXAMPLES Materials

Following is a list of materials, acronyms, and selected sources used inthe examples.

-   -   ADA: Adipic Acid (from INVISTA)    -   BDO: 1,4-Butanediol (from BASF, with a purity specification of        99.5 wt. %)    -   Phosphoric Acid: Phosphoric Acid (from Acros, grade/purity 98%)    -   TPT: Tetraisopropyl titanate (from DuPont, commercial Tyzor        grade)    -   PBT-co-adipate: Poly(butylene terephthalate-co-adipate)    -   PET: Poly(ethylene terephthalate)    -   Recycle PET: Recycle PET in the form of flakes or pellets was        obtained from a commercial vendor headquartered in India.

Methods and Procedures

The reported L*, a*, b* values were obtained through the diffusereflectance method acquired on a Gretag Macbeth Color-Eye 7000A with D65illumination. The term “white,” as used in this application, means thatthe material being described as white exhibits an L* value that is atleast 75, or at least 80, or at least 85 with a corresponding set of “a”and “b” values that are substantially close to 0, (less than 5 units onthe CIE color scale), where the “a” represents red and green hues and“b” represents blue and yellow hues of the white material on the CIE LABcolor scale. The L* value can range from 75, or 80, or 85 to 100. The“L*, a, b” method for describing colors is well known and developed bythe CIE (Commission Internationale de l'Eclairage). The CIE providesrecommendations for colorimetry by specifying the illuminants, theobserver and the methodology used to derive values for describing color3 coordinates are utilized to locate a color in a color space which isrepresented by L*, a* and b*. When a color is expressed in CIELAB, L*defines lightness, if a value is closer to 0 it means total absorptionor how dark a color is. If the L* value is closer to 100 it means totalreflection or how light a color is. a* denotes how green or red a coloris, whereas b* represents how blue or yellow a color is.

Intrinsic viscosity (I.V.) was determined with an automatic ViscotekMicrolab® 500 series Relative Viscometer Y501. In a typical procedure,0.5000 g of polymer sample was fully dissolved in a 60/40 mixture (byvol) of % phenol/1,1,2,2-tetrachloroethane solution (HarrellIndustries).

Dynamic scanning calorimetry (DSC), Perkin Elmer DSC 7 equipped withPyris DSC 7 software, was used to determine melting characteristics ofthe polymers synthesized as well as the thermal properties of thecorresponding monomers. In a typical procedure, a polymer sample (10-20mg) was heated from −50° C. to 200° C. (20° C./min), held at 200° C. for1 min, cooled back to −50° C. (20° C./min), then held at -50° C. for 1min, and the above heating/cooling cycle was repeated. The secondheating cycle is usually used to obtain the T_(g) and T_(m) data.

Example 1

The purpose of Example 1 was to prepare the polyester PBT-co-adipatederived from post-consumer PET, adipic acid (ADA), and 1,4-butanediol(BDO) using phosphoric acid as a catalyst quencher and hexamethylenediisocyanate as a chain extender. The materials, amounts, and reactionconditions are shown in Table 1.

TABLE 1 Materials and Conditions for Example 1. Scale of PhosphoricCatalyst EI EI Poly Poly Ex. Reaction PET:BDO ADA:BDO Acid Amount TempTime Temp. Time No. (g) (mol/mol) (mol/mol) (ppm) (ppm) (° C.) (min) (°C.) (min) 1 143 0.39 0.39 250 250 220 120 240 15

Techniques and Procedures

First, 50 grams of BDO and 36.5 grams of ADA were introduced into athree neck round bottom flask. The reactor was placed in an oil bath thetemperature of which was adjusted to 175° C. Then, 250 ppm of TPT wasadded to the reactor under inert atmosphere. The ester interchangetemperature was increased to 220° C. at a rate of 2° C./min whilestirring at 260 rpm under nitrogen. After the evolution of water ceased,excess butanediol was distilled out under reduced pressure. Then, 48grams of post-consumer PET and 50 grams of BDO were introduced into thereactor while stirring at 220° C. The mixture was heated over the courseof 2 hours. Then, 0.5 ml of phosphoric acid solution in water (0.1 g/ml)was added. The temperature of the reaction mixture was increased to 240°C. When all the PET flakes were melted, the vacuum was reduced to below1 torr. After achieving desired oligomers, the vacuum was stopped and0.7 ml of hexamethylene diisocyanate was added into the reactor. Themelt was mixed with hexamethylene diisocyanate for 15 minutes undernitrogen atmosphere. After achieving the desired intrinsic viscosity,the reaction was stopped.

Results

Table 2 shows the Tg, Tm, molecular weight data (obtained from gelpermeation chromatography (GPC) using polystyrene standards), intrinsicviscosity (I.V.), and color obtained from visual observation of Example1.

TABLE 2 Results for Example 1 IV Ex. (dL/ T_(m) T_(g) No. min) (° C.) (°C.) PDI Mn Mw L* a* b* 1 1.94 102 −22 6.8 41000 280000 75.8 0.9 11.8

Table 3 describes the compositional analysis of Example 1 obtainedthrough proton NMR. The number reported therefore reflects the degree ofincorporation of the named unit in the polymer.

TABLE 3 Compositional analysis result of Example 1 Ex. Isophthalic AcidTerephthalic acid ADA BDO EG No. (mol %) (mol %) (mol %) (mol %) (mol %)1 0.6 25.1 24.3 41.7 8.3

Discussion

A novel approach was used to prepare PBAT copolyesters derived throughpost-consumer PET. This approach includes first the preparation of theoligomers of PBAT made through the melt condensation of ADA, BDO, andPET in the presence of phosphoric acid catalyst quencher. The resultingoligomers exhibited white color due to lower reaction temperature andsuccessful quenching of catalyst. Then the oligomers were chain extendedusing hexamethylene diisocyanate at the same temperature and atmosphericpressure. A sharp viscosity increase was observed within 15 minutesindicating that chain extension through hexamethylene diisocyanate israpid and quantitative.

The results shown in Table 2 demonstrate that the current processenabled the co-polyester to obtain a very high IV. The meltingtemperature of Example 1 is 15° C. lower compared to a commercialPBT-co-adipate (T_(m)=117° C.) obtained from printed BASF data sheet.

The resulting copolyesters include isophthalic acid and EG in itsbackbone, which arises from the Recycle PET. The mole percent of EG molin the backbone is high compared to the PBT-co-adipate prepared from PETvia other process, likely due to lack of vacuum during the chainextension process.

All references cited herein are incorporated by reference in theirentirety. While typical embodiments have been set forth for the purposeof illustration, the foregoing descriptions should not be deemed to be alimitation on the scope herein. Accordingly, various modifications,adaptations, and alternatives can occur to one skilled in the artwithout departing from the spirit and scope herein.

1-15. (canceled)
 16. A poly(butylene terephthalate-co-adipate) copolymer having a melt temperature from 100 to 120° C., wherein the copolymer comprises a residue derived from a polyethylene terephthalate component selected from the group consisting of polyethylene terephthalate, polyethylene terephthalate copolymers, and combinations thereof; a residue of a quencher selected from the group consisting of a phosphorus-containing compound, a nitrogen-containing compound, a boron-containing compound, and combinations thereof; and from 0.05 to 1 weight % of a residue of a chain extender selected from the group consisting of isocyanurate, polyisocyanate, isocyanate and combinations thereof, wherein oligomers of poly(butylene terephthalate-co-adipate have been reacted with the chain extender; wherein the poly(butylene terephthalate-co-adipate) copolymer has a melting temperature of 100 to 120° C.; a number average molecular weight of at least 30,000 g/mole; an intrinsic viscosity of at least 1.0 deciliter per minute; and a T_(g) of −30 to −10° C.
 17. The copolymer of claim 16, comprising from 0.05 to 1 mol % of the quencher residue, based on the copolymer.
 18. The copolymer of claim 16, wherein residue derived from the polyethylene terephthalate component is selected from ethylene glycol groups, diethylene glycol groups, isophthalic acid groups, and combinations thereof.
 19. The copolymer of claim 16, wherein the copolymer comprises less than 10 mole % of ethylene glycol groups, based on poly(butylene terephthalate-co-adipate) copolymer.
 20. The copolymer of claim 16, wherein the copolymer comprises less than or equal to 2 mole % of isophthalate groups, based on poly(butylene terephthalate-co-adipate) copolymer.
 21. The copolymer of claim 16, wherein the copolymer comprises less than 10 mole % of a combination of ethylene glycol groups and isophthalate groups, based on poly(butylene terephthalate-co-adipate) copolymer.
 22. A composition comprising the poly(butylene terephthalate-co-adipate) copolymer of claim 16; and at least one of an additive selected from nucleating agents, antioxidants, UV stabilizers, plasticizers, epoxy compounds, melt strength additives, alcohols, acetates, alcohol-acetate copolymers, crosslinkers, anti-aging agents, retrogradation agents, anti-blocking agents, water, odor-controlling agents, and combinations thereof; and an additional thermoplastic polymer.
 23. The composition of claim 22, comprising from more than 10 to 59.99 wt. %, based on the total weight of the composition, of the poly(butylene terephthalate-co-adipate) copolymer of claim 16; from more than 40 to less than 89.99 wt. %, based on the total weight of the composition, of a polymer selected from aliphatic polyesters, aliphatic polycarbonates, starches, aromatic polyesters, cycloaliphatic polyesters, polyesteramides, aromatic polycarbonates, and combinations thereof; and from 0.01 to 5 wt. %, based on the total weight of the composition, of an additive selected from nucleating agents, antioxidants, UV stabilizers, plasticizers, epoxy compounds, melt strength additives, and combinations thereof; from 0.01 to 45 wt. %, based on the total weight of the composition, of an additive selected from alcohols, acetates, alcohol-acetate copolymers, and combinations thereof; and from 0.01 to 2 wt. %, based on the weight of the composition, of an additive selected from crosslinkers, anti-aging agents, retrogradation agents, anti-blocking agents, water, odor-controlling agents, and combinations thereof.
 24. The composition of claim 23, wherein the aliphatic polyester is selected from poly(lactic acid)s, poly(hydroxyalkanoate)s, poly(butylene succinate)s, poly(butylene adipate)s, poly(butylene succinate adipate)s, poly(caprolactone)s, and combinations thereof.
 25. An article comprising the composition of claim
 22. 26. The article of claim 25, wherein the article is a molding, film, fiber, or coating.
 27. (canceled)
 28. The composition of claim 16, wherein the quencher is selected from the group consisting of phosphoric acid, phosphorous acid, boric acid, nitrogen containing compound and combinations thereof.
 29. The composition of claim 16, wherein the chain extender is selected from the group consisting of mononuclear isocyanate, binuclear isocyanate, trinuclear isocyanate, tetra or higher nuclear isocyanate and their mixtures, diisocyanate selected from the group consisting of tolylene 2,4-diisocyanate, tolylene 2,6-diisocyanate, 2,4′-diphenylmethane diisocyanate, naphthylene-1,5-diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and methylenebis (2-isocyanatocyclohexane).
 30. The composition of claim 16, wherein the residue derived from a polyethylene terephthalate component is a dihydric alcohol selected from the group consisting of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, hexylene glycol, 1,3-cyclohexanedimethanol isomers, 1,4-cyclohexanedimethanol isomers, and combinations thereof.
 31. The composition of claim 16, wherein the residue derived from a polyethylene terephthalate component comprises a residue selected from the group consisting of dimethyl isophthalate, cyclohexane dimethanol, ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol groups, diethylene glycol groups, isophthalic acid groups and combinations thereof.
 32. A poly(butylene terephthalate-co-adipate) copolymer having a melt temperature from 100 to 120° C., wherein the copolymer comprises a residue derived from a polyethylene terephthalate component selected from the group consisting of polyethylene terephthalate, polyethylene terephthalate copolymers, and combinations thereof, wherein the residue derived from the polyethylene terephthalate component is selected from ethylene glycol groups, diethylene glycol groups, isophthalic acid groups, and combinations thereof; from 0.05 to 1 mol % of a quencher residue, based on the copolymer, wherein the quencher is selected from the group consisting of phosphoric acid, phosphorous acid, boric acid, nitrogen containing compound and combinations thereof, and combinations thereof; and from 0.05 to 1 weight % of a residue of a chain extender selected from the group consisting of isocyanurate, polyisocyanate, isocyanate and combinations thereof, wherein oligomers of poly(butylene terephthalate-co-adipate have been reacted with the chain extender; wherein the poly(butylene terephthalate-co-adipate) copolymer has a melting temperature of 100 to 120° C.; a number average molecular weight of at least 30,000 g/mole; an intrinsic viscosity of at least 1.0 deciliter per minute; and a T_(g) of −30 to −10° C. 